disassemble a tub faucet

i have an old leaky tub faucet [hot/shower/cold]. before i attempt to replace the washer or remove anything, what are the correct steps to disassemble it? i attached a pic of the type.
any assistance is appreciated.

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In the center of each handle is a little button that either prys off with a knife, or possibly unscrews. Then you will see a screw which holds the handle on. You might need a puller tool to actually pull the handle off.

The pyramid-shaped flanges will unscrew. Be very careful not to damage these as replacements may be diffficult to find.

Once the flange is off, turn off your water supply, and unscrew the entire stem from the body in the wall. Partially open each stem before trying to unscrew it. Take the stems to a good supply house for replacement, or at least new rubber parts. Also, get a stem wrench to unscrew the stem which is inside the body. It is the piece that the washer on the end of the stem contacts when you turn the faucet off. At the store, they should recognize the brand of stem and can give you the proper seat.

It is hard to be sure because of the angle, but it appears that this may be an old American Standard valve. If so, then the hex nuts on the back of the handles have to be unscrewed, (they will turn in "reverse" since they are on the backside of the handle), the the screw holding the handle adapters can be removed. The rest of it is fairly standared until you get the stem out. On the end should be a "Re-Nu" barrel which is also the seat. Replace it also, preferably with one that has an "O" ring seal if you can find one. When you put the faucet back together be sure to tighten it securely so that the Re-Nu barrel is firmly seated into the valve body. If not, then water will leak through it and destroy the valve body in short order and then you will have to replace the entire faucet.